The Aleph was a device invented by Professor Omen in 2268 to rid the galaxy of war. He described it as a "weapon of peace".

The Aleph was based on the concept of transfinite numbers, which were denoted by the first letter of the Hebrew alphabet, and named after a literary construct in a story by Jorge Luis Borges. Omen's device was a single point in space in which was contained all parts of the universe, possibly all universes. It appeared as a large spinning diamond, although the spinning was actually an illusion caused by the multiple images moving across its surface. Any object which came into contact with the Aleph was instantly transported to another universe at random. Anyone who looked into the Aleph would see everything in the universe simultaneously without confusion or overlapping. This would eventually cause loss of one's sense of self unless one possessed sufficient mental discipline, such as a Vulcan.

Omen used several Alephs to transport several Klingon, Romulan and Federation starships to other universes. The USS Enterprise was assigned to investigate the disappearances and discovered Omen was responsible. He revealed that he intended to blackmail the interstellar states into disarmament or have their starships vanish. When the Enterprise attempted to stop him, it was struck by an Aleph which transported the ship and itself to an empty pocket universe. With the ship's and crew's energies being drained, the Enterprise was forced to go through the Aleph to another universe, one in which intelligent life never evolved on Earth and space was controlled by Klingees. After studying the Aleph, the Enterprise crew was able to return to its original universe and confront Omen, who used an Aleph to send himself into another universe, taking the secret of their construction with him. (TOS novel: The Starship Trap)

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